This invention relates generally to transferring data packets between a telephony endpoint and a wide or local area network and more particularly to a secondary bus provided in a personal computer (PC) server-based platform for increasing the capacity for processing and transferring voice data.
Referring to FIG. 1, a conventional PC host platform 12 includes a PC host motherboard 22 coupled through a PC backplane such as a PCI or ISA bus 20 to various peripheral cards 24. Commercially available Internet-based packet-voice products are referred to generally as telephony endpoint cards 16. The packet-voice products 16 are used to convert analog voice signals from a telephone line 18 to digital data. A number of existing PC-based voice products are based on either ISA or PCI bus telephony cards which connect to the PC backplane bus 20 and interconnect through a TDM bus such as the Dialogic SC bus.
A router card 14 includes a local area network (LAN) interface and a wide area network (WAN) interface for coupling the PC host 22 to different network systems. The telephony cards 16 currently provide no direct Internet Protocol (IP) packet handling or routing functions, and rely on the PC host 22 for performing all packet processing. After the packet processing of the voice data is completed by the PC host 22, the voice packet data is transferred over a LAN or WAN system through router card 14.
One of the principle problems with PC-based packet handling is timely delivery of delay-sensitive voice traffic. In a PC, the simplest solution is to transfer all of the data from the voice endpoint cards 16 across the ISA or PCI bus 20 to a main processor on the PC host motherboard 22. Significant latencies exist in the voice card/host bus transfer, interrupt service and application scheduling, packet treatment logic (e.g., real-time transport protocol (RTP) packetization), transfer through the host computer stack and host processor/NIC bus transfer.
While manageable in internet phone terminals, latencies do not scale well to servers with tens or hundreds of endpoints. Since the host CPU in motherboard 22 and the PC backplane bus 20 are shared resources, performance is throttled for high-end routing applications.
Accordingly, a need remains for improving performance of telephony data handling in PC-based server platforms.